1. Field of the Invention
The present invention relates to a pair of binoculars with a vibration reduction mechanism by which an object to be observed can be seen as being substantially at a standstill, even when a hand of the observer is shaking.
2. Related Background Art
Conventional binoculars with a vibration reduction mechanism are disclosed, for example, in Japanese Patent Laid-Open Application No. 54-23554 and No. 7-43645.
A binoculars disclosed in the former application are provided with a pair of right and left objective lenses, a pair of right and left eye pieces, a pair of right and left erect prisms arranged between the pair of right and left objective lenses and the pair of right and left eye pieces, a single prism support frame for supporting this pair of right and left erect prisms, a gimbal support device for supporting the prism support frame as being rotatable around two axes which cross each other at right angles on a plane perpendicular to the optical axis, and a gyroscopic motor which is attached to a lens support frame.
A binoculars disclosed in the latter application is provided with a pair of right and left objective lenses, a pair of right and left eye pieces, a pair of right and left variable vertical angle prisms which are arranged between the pair of right and left objective lenses and the pair of right and left eye pieces, a sensor for detecting a vibration of the main body, a plurality of actuators for driving the pair of right and left variable vertical angle prisms, and a control circuit for determining an amount of drive of each of the actuators based on the vibration detected by the sensor.
The prior technology disclosed in the above-mentioned Japanese Patent Laid-Open Application No. 54-23554 is superior in that the pair of right and left erect prisms are supported by the single prism support frame and driven by the single gyroscopic motor so that the drive mechanism can be simplified. However, according to this prior technology, if, for example, the prism support frame is rotated around the axis in the vertical direction located midway between the right and left erect prisms due to a horizontal vibration so that the erect prism of the left optical system is moved to the object lens side and the erect prism of the right optical system to the eye piece side, a distance between the objective lens and the erect prism of the left optical system becomes different from a distance between the objective lens and the erect prism of the right optical system, so that a visibility of the right optical system becomes different from that of the left optical system. In other words, according to the prior technology, there arises a problem in that the mutual positional relationship among the plurality of optical components which constitute the right optical system turns out not to be identical with the mutual positional relationship among the plurality of optical components which constitute the left optical system for a vibration in the horizontal direction, and the visibility of the right optical system becomes different from that of the left optical system. Further, according to this prior technology, in order to reduce a swinging diameter of the erect prism so as to reduce the difference between the visibility of right and left optical systems and also to reduce the size of the binoculars, it is required to arrange the right and left erect prisms substantially midway between the right and left objective lenses and the right and left eye pieces. Accordingly, an erect prism of a comparatively large size is required and, as a result, there also arises a problem in that the size of the pair of binoculars is increased and the degree of freedom in designing the optical systems is limited.
On the other hand, according to the prior technology disclosed in the latter Japanese Patent Laid-Open Application No. 7-43645, the right and left variable vertical angle prisms are driven independently of each other so that the problems of the former prior technology are not brought about. However, since the right and left variable vertical angle prisms are driven independently of each other, there arises a different problem in that the drive mechanism becomes complicated so as to increase the cost as well as the size thereof.